High speed down-link packet access (HSDPA) is a key feature in new generations of wireless communications for wideband CDMA (W-CDMA). HSDPA will provide bit rates up to approximately 20 Mbps. This is sufficient for multi-media services. To achieve this high bit rate, multiple HSDPA receivers share a single channel in both time and code domains.
With HSDPA, it is possible to achieve higher bit rates when the receivers include a multi-path interference canceller (MPIC), see Higuchi et al., “Multipath Interference Canceller for High-Speed Packet Transmission with Adaptive Modulation and Coding Scheme in W-CDMA Forward Link,” Proc. of IEEE VTC2001, May 2001, and NTT DoCoMo, “Multipath Interference Canceller (MPIC) for HSDPA and Effect of 64QAM Modulation,” 3GPP TSGR1#18(01)010.
Intra-cell interference is due to multiple channelization code spreading and common pilot channel (CPICH) signals in a multi-path fading environment. When the HSDPA signal uses higher order modulation, throughput gains are only attainable in a single path environment, see Panasonic, “Interference cancellation for HSDPA: an option or a requirement?,” 3GPP TSGR1#21(01)0905. Therefore, HSDPA receivers should include an MPIC to provide meaningful performance gains.
In addition, there are other sources of interference which degrade performance in multipath fading environments. Typically, the performance of a high-speed down-link shared channel (HS-DSCH) reaches an error floor at 10% of frame error rate (FER) for higher order modulation, when both voice signals and high bit rate data services are supported using code division multiplexing.
In the prior art, MPIC has been done, but only for high bit rate data signals, see Kawamura et al., “Comparison Between Multipath Interference Canceller and Chip Equalizer in HSDPA in Multipath Channel,” Proc. Of IEEE VTC2002-Spring, May 2002. Canceling high bit rate data signals is relatively simple, because the channelization codes are known.
However, to cancel all interference, voice and low bit rate data signals also need to be considered. This is more difficult, because the chanelization codes for these signals are not known for the HSDPA receivers. Therefore, to increase the system capacity, it is important for HSDPA receiver to cancel all intra-cell interference including voice signals, low bit rate signals, high bit rate data signals, and common pilot channel signals.